Sterilization/disinfection cycle control

ABSTRACT

A sterilizer includes a vacuum chamber, a source of vaporizable sterilant, a vacuum pump, and a control system. The control system is programmed to take one or more data inputs regarding the nature of the load, such as lumen length and diameter, and determine one or more parameters of the sterilization cycle based upon the inputs.

BACKGROUND OF THE INVENTION

This application relates to cassettes for delivering sterilant to aninstrument sterilizer, and more particularly to such cassettes havingencoded thereon a machine readable lumen claim.

One popular method for sterilizing instruments, such as medical devices,is to contact the devices with a vapor phase chemical sterilant, such ashydrogen peroxide. In many such sterilizers, it is preferred to deliverthe sterilant in liquid form and vaporize it in the sterilizer. Oneparticularly convenient and accurate method for delivering the liquidsterilant is to put a predetermined quantity of sterilant into acassette and deliver the cassette to the sterilizer. The sterilizer thenautomatically extracts the sterilant from the cassette and uses it forsterilization procedure. Typically, such a cassette would entailmultiple cells containing equal amounts of liquid sterilant with asterilization procedure employing the sterilant from one or more cells.Such a system is currently available in the STERRAD® sterilizationsystem available from Advanced Sterilization Products in Irvine, Calif.

U.S. Pat. Nos. 4,817,800; 4,869,286; 4,899,519; 4,909,287; 4,913,196;4,938,262; 4,941,518; 5,882,611; 5,887,716; and 6,412,340, eachincorporated herein by reference, disclose such cassettes and a methodfor draining liquid sterilant from a cell within a cassette.

Flexibility in controlling such machines has typically been lacking andtypically they have a single fixed cycle. It is believed that some steamsterilizers may employ two, or perhaps more, fixed user selectablecycles. Even here the user must himself or herself choose the cycle. Themachine does not determine the cycle for the user. The present inventionovercomes these and other limitations in the prior art.

SUMMARY OF THE INVENTION

A sterilizer according to the present invention for sterilizing a loadof instruments in a sterilization cycle comprises a vacuum chamber, asource of vaporizable sterilant, a vacuum pump, and a control system.The control system is programmed to take one or more data inputsregarding the nature of the load and determine one or more parameters ofthe cycle based upon the one or more data inputs.

The data inputs can include a material of one or more instruments in theload. For instance, the control system can be programmed to increase theamount of sterilant input to the vacuum chamber from the sterilantsource in response to the input of a material of one or more instrumentsin the load where that material is absorbent of the sterilant. Suchmaterials include: a polyamide, a polyurethane, a silicone rubber, apolyvinyl chloride, a polymethyl methacrylate or a polysulfone. In oneaspect of the invention, the control system is programmed to enhance aportion of the sterilization cycle designed to eliminate sterilantresiduals when the material is absorbent of the sterilant.

Preferably, the one or more data inputs comprise a length and internaldiameter of a lumen. They could also include the weight of the load andan indication of whether the load contains items enclosed by asemi-permeable barrier, such as by being wrapped in CSR wrap or enclosedin pouches.

The parameters of the sterilization cycle which can be varied includethe concentration of sterilant, the time of exposure to the sterilant,the level of the vacuum, and whether and how vigorously to employ aresiduals reduction step.

In one aspect of the invention, the control system is programmed toprovide a higher concentration of sterilant to the cycle for lumens of aparticular internal diameter which exceed a predetermined length.

The data can be manually input by the user, such as via a touch screenor keyboard, or some or all of it can be read automatically from theinstruments, such as by reading a barcode or RFID tag on the instrument.

A feedback control loop in connection with sensor input about the cyclecan be used to adjust one or more of the sterilization cycle parameters.Inputs might include pressure, temperature and sterilant concentrationwithin the vacuum chamber.

A method according to the present invention of sterilizing a load ofinstruments in a sterilizer comprises the steps of: entering dataregarding the nature of the load into a control system of thesterilizer; placing the load into a vacuum chamber in the sterilizer;drawing a vacuum upon the vacuum chamber with a vacuum pump; admitting asterilant into the vacuum chamber, the sterilant being substantially inits vapor phase within the vacuum chamber, and contacting the load withthe sterilant; and based upon the data regarding the nature of the loadentered into the control system, determining one or more parameters ofthe cycle.

The efficacy of sterilization can be verified with a biologicalindicator. It can also be verified by measuring exposure level andintegrating this over time to ensure that at least a minimum integratedexposure of the load to the sterilant is achieved.

In one aspect of the invention, a cycle outline is saved for future usewith a similar load. The cycle outline can be saved in many fashionssuch as the data inputs, or the resulting cycle parameters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a sterilizer employing a cassette accordingto the present invention;

FIG. 2 is a rear perspective view of a cassette handling systemaccording to the present invention;

FIG. 3 is a front perspective view of the cassette handling system ofFIG. 2;

FIG. 4 is a front perspective view of the cassette handling system ofFIG. 2 showing a spent cassette collection box;

FIG. 5 is a rear perspective view of the cassette handling system ofFIG. 2 showing its carriage in the insert position;

FIG. 6 is a rear perspective view of the cassette handling system ofFIG. 2 showing its carriage as it moves toward the home position;

FIG. 7 is a rear perspective view of the cassette handling system ofFIG. 2 showing its carriage in position to read a bar code on thecassette;

FIG. 8 is a rear perspective view of the cassette handling system ofFIG. 2 showing its carriage in the home position;

FIG. 9 is a front perspective view of the cassette handling system ofFIG. 2 showing its carriage in position to tap the cassette's firstcell;

FIG. 10 is a cross sectional view of the cassette showing a celltherein;

FIG. 11 is a front perspective view of the cassette handling system ofFIG. 2 showing upper and lower needles on an extractor subsystempenetrating the first cell of the cassette;

FIG. 12 is a front perspective view of the cassette handling system ofFIG. 2 showing upper and lower needles on the extractor subsystem inposition to penetrate the last cell of the cassette;

FIG. 13 is a front perspective view of the cassette handling system ofFIG. 2 showing the cassette being ejected therefrom;

FIG. 14 is a flow chart of the cassette handling process;

FIG. 15 is a rear perspective view of an alternative embodiment of acassette handling system of the present invention employing RFIDtechnology;

FIG. 16 is a memory map of an RFID tag of the cassette shown in FIG. 15;

FIG. 17 is a top plan view of an unfolded blank for forming the spentcassette collection box of FIG. 4; and

FIG. 18 is a perspective view of the blank of FIG. 17 folded to form thespent cassette collection box.

DETAILED DESCRIPTION

Sterilizer Overall Configuration

FIG. 1 shows in block diagram form a vapor phase sterilizer 10 employinga cassette handling system 12 according to the present invention. Thesterilizer 10 comprises a vacuum chamber 14 and a vacuum pump 16 forexhausting atmosphere therefrom. A vaporizer 18 receives liquidsterilant from the cassette handling system 12 and supplies it in vaporform to the vacuum chamber 14. A screen grid electrode 20 is providedwithin the vacuum chamber 14 for exciting the contents into the plasmaphase during a portion of the sterilization cycle. A micro filtered vent22 and valve 24 allow sterile air to enter the vacuum chamber 14 andbreak the vacuum therein. A control system 28 ties in to all of themajor components, sensors and the like within the sterilizer 10 tocontrol the sterilization cycle.

A typical sterilization cycle might include drawing a vacuum upon thevacuum chamber 14 and turning on power to the electrode 20 to evaporateand extract water from the vacuum chamber 14. The electrode 20 is thenpowered off and a low vacuum of less than 1 torr drawn on the vacuumchamber 14. Sterilant, such as hydrogen peroxide solution, is vaporizedby the vaporizer 18 and introduced into the vacuum chamber 14 where itdiffuses into contact with the items to be sterilized and killsmicroorganisms thereon. Near the end of the cycle, power is againapplied to the electrode 20 and the sterilant is driven into the plasmaphase. The electrodes 20 are powered down and filtered air is drawn inthrough the valve 24. This process can be repeated. The Jacobs et al.U.S. Patent Application, Publication No. 20030235511, incorporatedherein by reference, illustrates in detail such a cycle.

Cassette Handling System

Turning also to FIGS. 2 to 4, the cassette handling system 12 accordingto the present invention is shown. It comprises in gross, a carriage 32for holding a cassette 34, a lead screw 36 and motor 38, an extractorsubsystem 40 and a scanner 42.

The carriage 32 comprises a bottom panel 44, a side panel 46 and toppanel 48 along with small vertical flanges 50 and 52 on the top andbottom and top panels 48 and 44, respectively, to capture the cassette34. The bottom, side and top panels 44, 46 and 48 flare outwardly at anentrance 54 of the carriage to aid in insertion of the cassette 34. Twospring catches 56 on the flanges 50 and 52 engage irregular surfaces ofthe cassette 34 to firmly position the cassette 34 within the carriage32.

The carriage 32 travels along the lead screw 36 and is supported on anupper rail 58. A lead screw nut 60 attached to the bottom panel 44 andhaving a threaded opening 62 and an unthreaded opening 63 receives thelead screw 36 and effects horizontal movement of the carriage 32 inresponse to rotations of the lead screw 36. Flanges 64 extend outwardlyfrom the top panel 48 and flanges 66 extend outwardly from the sidepanel 46 each having openings 69 for receiving the upper rail 58. Themotor 38 is preferable a stepping motor and connects to the lead screw36 to precisely control the horizontal position of the cassette 34relative to a frame 68.

The extraction assembly 40 comprises an upper needle 70 and a lowerneedle 72, each being of a lumened configuration. The upper needleconnects to an air pump 74 which can force air out through the upperneedle 70. The lower needle 72 connects to a valve 76 and from there isplumbed to the vaporizer 18.

The scanner 42 is oriented so as to be able to read a barcode 80 on thecassette 34 as well as a barcode 82 on a spent cassette collection box84. Upon insertion of the cassette 34 into the carriage 32 the scanner42 reads the cassette barcode 80. The barcode 80 is preferably encodedwith information regarding the contents of the cassette 34, includinglot numbers and expiration dates. This information can be used todetermine whether the cassette 34 is fresh and of the correct type andwhether the cassette 34 has been used in the system before and thus isat least partially empty. The code is communicated to the control system28 which makes these determinations.

The scanner 42 can also see the spent cassette collection box barcode 82when the carriage 32 moves inwardly and away from the scanner 42. Eachspent cassette collection box 84 preferably has two barcodes 82, one ineach opposing corner so that the scanner 42 can see one of themregardless of which end of the spent cassette collection box 84 isinserted first. With the spent cassette collection box 84 filled, thespent cassettes 34 block the barcode 82 which alerts the control system28 that there is no capacity for receiving additional spent cassettes34. Preferably this message will be output to a user, such as on adisplay screen (not shown). If the cassette 34 is empty it will not beejected and no new cycles will be run until a spent cassette collectionbox 84 having capacity to receive a spent cassette 34 is placed into thesterilizer 10.

A forward flag 86 and rearward flag 88 project outwardly and downwardlyfrom the carriage side panel 46. They slide through a slot 90 in a slotsensor 92 which detects their presence within the slot 90, such as byblocking a beam of light. Travel of the front flag 86 and rear flag 88through the slot sensor 92 provides a reference location of the carriage32 to the control system 28.

The top panel 48 of the carriage 32 can rotate about the upper rail 58.A spring 94 between the top panel 48 and side panel 46 biases the toppanel 48 downwardly to hold the cassette 34 within the carriage 32. Adisposing cam 96 sits behind the side panel 46 and aligns with anejecting tab 98 which extends outwardly and downwardly from the toppanel 48 and which can project through an opening 100 in the side panel46 when the top panel 48 rotates upwardly. Such rotation of the toppanel 48 releases its hold upon the cassette 34 and due to the ejectingtab 98 projecting through the opening 100 pushes the cassette 34 out ofthe carriage 32 and into the spent cassette collection box.

The disposing cam 96 controls rotation of the top panel 48. It comprisesa generally triangular shape, having an outwardly facing side 102,forwardly facing side 104 and rearwardly facing side 106. Turning alsonow to FIG. 5, it mounts for rotation upon an upwardly extending spindle108. A spring 110 biases the disposing cam 96 counterclockwise, urgingthe outwardly facing side 102 into contact with an abutment 112. Inwardmovements of the carriage 32 allow the ejecting tab 98 to cam over therearwardly facing side 106 of the disposing cam 96, thus allowing thedisposing cam 96 to rotate clockwise and allow the ejecting tab 98 topass thereby without effecting rotation of the top panel 48. However,outward movement of the carriage 32 causes the ejecting tab 98 to camover the forwardly facing side 104 of the disposing cam 96. During suchmotion contact between the outwardly facings side 102 of the disposingcam 96 and the abutment 112 prevents rotation of the disposing cam 96.The camming of the ejecting tab 98 thus causes it to move laterallytoward the side panel 46 thereby rotating the top panel 48 upwardly andreleasing the cassette 34 from the carriage 32.

Prior to inserting the cassette 34 the carriage 32 is fully retracted toits outward position (to the left as shown in FIG. 5). In this positionalso, a forward end 114 on the lead screw nut 60 engages a stop 116 thuspositively locating the position of the carriage 32. Turning also now toFIG. 6, manual insertion of the cassette 34 causes the carriage 32 tomove inwardly (to the right as shown in FIG. 6) and moves the front flag86 into the slot sensor 92. This movement is preferably caused by thephysical force from inserting the cassette 34, however, a torque orother sensor could be applied to allow the stepping motor 38 to takeover this movement upon feeling the force of the cassette 34 beinginserted into the carriage 32. Allowing this movement to come from theforce of the insertion of the cassette 34 ensures that the cassette 34is fully seated within the carriage 32 before the movement begins.

Once the front flag 86 is read by the slot sensor 92 the stepper motor38 takes over and starts to move the carriage 32 inwardly. Turning alsonow to FIG. 7, during this stage, the scanner 42 scans the barcode 80 onthe cassette 34. The control system 28 interprets the information comingfrom the barcode 80 and determines whether the cassette 34 has been usedin the sterilizer 10 before, whether the cassette contains freshsterilant, and other data as appropriate. Preferably, the information onthe barcode 80 is encrypted to prevent unauthorized parties fromcreating cassettes which may not meet the quality standards necessaryfor proper sterilization.

If the control system 28 rejects the cassette 34 a carriage 32 is movedsufficiently inwardly so as to pass the ejecting tab 98 past thedisposing cam 96 and is then moved back to the insertion position shownin FIG. 5 to eject the rejected cassette 34. If the cassette 34 isaccepted, the carriage 32 continues inward movement to the home positionas shown in FIG. 8 in which the rear flag 88 has just passed out of theslot sensor 92.

Turning also now to FIGS. 9 and 10, the cassette 34 comprises aplurality of cells 118 containing liquid sterilant 120. Variousstructures of a cassette may be employed. The cassette 34 showncomprises a hard outer shell 122, preferably formed of an injectionmolded polymer, such as high impact polystyrene, high densitypolyethylene or high density polypropylene, which encloses theindividual cells 118, the cells 118 being formed of a blow moldedpolymer such as low density polyethylene. However, a more rigid materialcan be used to form the cassette cells 118 in which case the outer shell122 could be omitted. In the cassette 34 shown, an upper aperture 124and lower aperture 126 through the shell 122 allows the upper and lowerneedles 70 and 72 to penetrate the shell. The cell 118 is formed of amaterial easily penetrated by the needles. If the cell 118 is formed ofa more substantial material, a thinning of the material could beprovided at the locations to be penetrated by the needles 70 and 72.

The control system 28 uses the home position of FIG. 8 as a referenceposition for positioning the various cells 118 in front of the extractorsubsystem 40. By moving the carriage 32 a predetermined amount from thehome position a given cell 118 can be brought to face the extractorsystem 40. In FIG. 9, cell one has been placed in front of the extractorsystem 40. Turning also now to FIG. 11, an actuator 128 drives theextractor subsystem 40 toward the cassette 34 causing the upper andlower needles 70 and 72 to penetrate the upper and lower apertures 124and 126 and enter the cell 118. After the needles have fully extended,the air pump 74 drives air into the cell 118 through the upper needle70. The system waits a couple of seconds before starting the air pump 74and opening the valve 76 to ensure proper placement and settling of theneedles within the cell 118. The sterilant 120 flows out through thelower needle 72 and is piped off to the vaporizer 18. After a sufficienttime to extract the sterilant 120, the air pump 74 switches off and theactuator retracts the extractor subsystem 40 from the cassette 34.

The vaporizer 18 connects to the vacuum chamber 14 which allows thelower needle 72 to easily be placed at a pressure below atmospheric.Thus, the pump 74 can optionally be replaced by a valve (not shown) opento atmosphere, in which case the incoming atmospheric pressure air willprovide the driving force to empty the cell 118.

Rather than employ upper and lower needles 70 and 72, one needle havingtwo lumens therethrough would suffice. One of the lumens would providepressurizing gas and one would extract liquid sterilant. A furtheralternative arrangement would be to pierce the cell 118 vertically, orsubstantially so, from an upper part of the cell 118, preferably withsuch a double lumen needle. This would minimize leakage around the holecreated by the needle entering the cell 118. Such entry would also allowthe tip of the needle to come closer to the lowest point of the cell 118for maximum extraction efficiency. If one desired to extract less thanall of the contents of the cell 118, one method would be to position theneedle extracting the sterilant, such as the lower needle 72 or the justmentioned double lumen needle, at the level in the cell 118 down towhich extraction is desired. Liquid sterilant above the position wouldbe extracted and sterilant below would remain. This would beparticularly convenient with the just mentioned vertically travelingneedle.

Turning also to FIG. 12, each time the control system 28 determines thata new dose of sterilant 120 is required, the stepper motor 38 moves thecassette to position the next cell 118 in front of the extractorsubsystem 40 and a new extraction takes place. Multiple extractions maybe employed for a given sterilization cycle. When the cassette 34 hasbeen depleted, the carriage 32 moves towards the insert position thuscausing the ejecting tab 98 to cam over the disposing cam 96 to rotatethe top panel 48 upwardly and project the ejecting tab 98 through theopening 100 to drive the cassette 34 out of the carriage 32 as describedabove and as shown in FIG. 13. The cassette 34 falls into the spentcassette collection box 84 and the carriage 32 returns to the insertionposition as shown in FIG. 5.

The foregoing discussion described the operation of the cassettehandling system in some detail. FIG. 14 shows, in block diagram form,the basic operation of the cassette handling system 12.

Lumen Claim

Typically, sterilizers and their cycle parameters have been optimized toenable sterilization of the most challenging loads possible so as to notunduly restrict which devices might be sterilized therein. Long narrowlumens being one of the most challenging areas to sterilize have becomethe de facto standard in defining the potency of a sterilizationprocess, i.e. its ability to sterilize devices having a lumen of acertain diameter and length. The longer and narrower the lumen which canbe sterilized, the more efficacious the sterilizer cycle. A sterilizeris thus said to achieve a lumen claim of lumen diameter by lumen length,as for instance 1 mm×100 mm. The lumen claim can also include thematerial forming the lumen. Typically, the lumen claim will be the claimwhich has been approved by a regulatory agency such as the US Food andDrug Administration, but can represent merely the lumen which thesterilizer and cycle can effectively sterilize. Typically, sterilizationentails a six log reduction in the challenge microorganisms. In hydrogenperoxide based sterilization systems the preferred challengemicroorganism is Geobacillus stearothermophilus.

Rather than always run the sterilizer to achieve its maximum lumenclaim, it may be desirable to run the sterilizer 10 in different cyclesdepending upon the devices loaded therein for sterilization. Preferably,an operator selects a lumen claim when loading the sterilizer 10 basedupon the most challenging lumen device being loaded and then enters thatlumen claim into the control system 28. Alternatively, the devices canbe coded themselves, such as with a bar code which is scanned as thedevice is loaded, and the control system 28 selects the appropriatecycle to meet a particular lumen claim based upon the most challenginglumen device which was scanned. A set of lumen claim cycles programmedinto the sterilizer might include the following: a) 1 mm×1,000 mm, b) 1mm×500 mm, c) 2 mm×100 mm, and d) no lumen. The cycles for the lessdemanding lumen claims can be adjusted, such as injecting lesssterilant, employing a lower concentration sterilant, a shorter contacttime, or a less demanding vacuum (higher pressure). In general,employing a lower concentration sterilant can provide benefits ingentler processing of the instruments to be sterilized.

To provide flexibility in optimizing differing lumen sterilizationcycles, preferably cassettes 34 having loads of sterilant optimized fora given lumen claim cycle are provided. Preferably, the lumen claim isencoded onto the barcode 80 along with other data such as the sterilizermodel for which the cassette 34 is intended and the expiration date.

A suggested data layout for the barcode 80 comprises the followingfields: a) sterilizer model for which the cassette 34 is intended (threebinary digits—associated with a look-up table); b) expiration date(eight binary digits representing the number of months from a fixeddate); c) lumen claim (three binary digits—associated with a look-uptable). Alternatively, the lumen claim could be represented by separatelumen internal diameter and length fields, preferably in millimeters anddecimeters respectively. Further, as illustrated in the last row ofTable 1a some lumens having different dimensions may nonetheless haveequivalent processing requirements. Preferably, one of the equivalentlumens would be coded onto the barcode 80, with the sterilizer's controlsystem being programmed with the equivalents. Many coding schemes arepossible within the scope of the invention.

Tables 1a and 1b illustrate how certain parameters of the cycle can bemodified to treat particular lumens.

TABLE 1a 173L chamber with two loads Time required to kill about 1 × 10⁶Geobacillus Peroxide Peroxide stearothermophilus Device concentrationamount spores Stainless steel 59% wt   1 g  5 minutes Surface 1 mm ×1000 mm 50% wt   2 g 15 minutes TEFLON* lumen 1 mm × 125 mm, 59% wt 1.7g 20 minutes 2 mm × 250 mm or 3 mm × 400 mm Stainless Steel lumen*polytetrafluoroethylene, TEFLON is a trademark of 3M Co.

TABLE 1b 51L chamber with one load Time required to kill about 1 × 10⁶Geobacillus Peroxide Peroxide stearothermophilus Device concentrationamount spores 2 mm × 400 mm 90% wt 0.23 g 3 minutes Stainless Steellumen 1 mm × 150 mm 90% wt 0.34 g 3 minutes Stainless Steel lumen 1 mm ×500 mm 90% wt 0.45 g 7 minutes Stainless Steel lumen 1 mm × 350 mm 90%wt 0.45 g 3 minutes TEFLON* lumen *polytetrafluoroethylene, TEFLON is atrademark of 3M Co.

Beyond merely entering lumen data, the control system 28 can beconfigured to take multiple inputs and use this information to determinehow a subsequent sterilization cycle should be performed. Such inputscan include: whether the load is wrapped or unwrapped (such as inCentral Supply Room “CSR” wrap), the weight of the load, the number ofitems (and more preferably the number of certain types of items such asrigid or flexible endoscopes, the materials of the load, such as theproportion of plastics, the presence or proportion of polymers highlyabsorptive of hydrogen peroxide such as, but not limited to, polyamides,polyurethanes, silicone rubbers, PVCs, Polymethyl methacrylates andpolysulfones, and whether full sterilization or merely high leveldisinfection is needed. Some of these inputs can be determined by themachine with addition of appropriate sensors, such as for example theweight of the load which can be determined via some form of scalepreferably incorporated into the sterilizer 10 or via measuring plasmapower.

The sterilizer 10 has many sensors including those to measuretemperature, pressure, sterilant concentration and plasma power. Thesein conjunction with the user inputs are used by the control system toadjust the parameter of the sterilization cycle in order to adequatelytreat the load in the most efficient manner. Table 2 illustrates how acycle can be modified to for several user inputs.

TABLE 2 Cycle Response to User Input Attributes of load Response Controlmechanism Sterilization or high High level disinfection - Determinelevel disinfection low sterilant concentra- sterilant/disinfectant tionor/and mass/shorter concentration level exposure time and quantity toSterilization - high reach sterilant level sterilant concentrationrequired. Monitor or/and mass concentration/ amount by sterilant sensorand maintain at the required level Wrapped or unwrapped Unwrapped - lowDetermine load concentration/mass sterilant/disinfectant deliveryconcentration level Wrapped - higher and quantity to concentration/massreach sterilant delivery level required. Monitor concentra- tion/amountby sterilant sensor and maintain at the required level Load volume andweight High volume: possibly Monitor and main- more absorption tain therequired High weight: possibly sterilant/disinfectant highercondensation concentration level. Set temperature at higher level toreduce absorption and condensation effects. Preheat the load ifnecessary. High venting/ residual removal treatment. Loads containsmaterials Higher injection Monitor and main- that are a decomposer ormass/concentration and tain the required absorber to the temperature maybe sterilant/disinfectant sterilant/disinfectant required level. Highventing/ residual removal treatment if ex- cessive absorb is present(Identify from sterilant concentration sensor output) Load containslumens: High concentration and/ Set concentration short vs. long ormass, longer exposure and pressure time and pre-processing gradientlevels pressure gradient accordingly

In one aspect of the invention, the user would first choose betweenrunning one or more standard cycles, or one or more user programmedcycles, or enter load and process data to design a cycle. Under theoption of entering load data the user could first select whethersterilization or high level disinfection is required. If sterilizationis selected, the user would preferably enter whether the load containedwrapped containers or items. The user would second enter whether theload contained lumens or not. For a load lacking lumens the overallweight and materials in the load would be entered. These entries couldbe made item by item, or as an aggregate. For lumens, additional datasuch as the lumen length and internal diameter would be entered. Again,this data could be entered as the most challenging single lumen, or itemby item. Thirdly, the user would enter load preparation information suchas whether preheating or moisture removal steps should be taken with theload. Alternatively, the control system could recommend or determinewhether these steps should be taken based upon the data entered. Thesesteps can lengthen the overall process time and in some instances theuser may wish to opt out of their use to speed the cycle. Fourth, theuser would enter data as to the source of sterilant (bulk or cassette),sterilant concentration, sterilant volume and type of sterilant. Again,some of this could rather be recommended or determined by the controlsystem based upon the entered data, which could also provide the userwith a message as to which type of cassette should be loaded forinstance. Finally, information about residual removal would be entered,i.e. whether a residual removal step should be taken at the end of thecycle and whether heat, plasma, sterile air purging, vacuum or somecombination thereof should be employed. Again, this information couldrather be recommended or determined by the control system based upon thedata entered. The user would have the option of saving this cycle set-upso that it could be chosen from a cycle menu for later cycles of similardevices. Names could be provided to the cycle set-up, such as byprocedure instrument set, to allow easy retrieval of the appropriatecycle in the future.

Determinations of cycle changes can be made based upon table look-upsemploying cycle corrections based upon known cycle modifications relatedto load modifications, preferably backed up by test data. For instance,tests run on lumens of varying diameter and ID can determine exposuretimes and sterilant concentrations that produce reliable sterilization.In addition, calculations of integrated sterilant exposure (quantity andtime) can be employed. For instance, experiments have shown that aparticular lumen can be successfully sterilized by a particularintegrated sterilant exposure; varying the quantity or time whilemaintaining the overall integrated exposure still achieves a reliablesterilization.

The system of reading barcodes on the cassette 34 and spent cassette box84 can be replaced with radio frequency identification tags, commonlyknown as RFID tags. An RFID system 130 is shown in FIG. 15. It comprisesa controller 132 connected via an SPDT reed relay 134 to a cassetteinsertion antenna 136 located on the carriage 32 and a cassette disposalantenna 138 located beneath the spend cassette box 84. Each cassette 34carries a cassette RFID tag 140. Similarly, each spent cassettecollection box 84 carries a collection box RFID tag 142. Preferably, thecontroller 132 comprises a Texas Instruments multifunction reader moduleS4100 and the RFID tags 140 and 42 comprise Texas Instruments RFID tagRI-101-112A each of which are available from Texas Instruments, Dallas,Tex.

The control system 28 (FIG. 1) selects one of the antennas, as forinstance the cassette insertion antenna 136 and sends a signal to therelay 134 to engage this antenna with the RFID controller 132. Theantenna reads the information stored on the cassette insertion RFID tag140 which identifies the cassette 34 and its contents. The informationread is similar to the information read using the barcode, howeverpreferably, the RFID tag 140 has the ability to update the informationstored thereon. Accordingly, additional data such as the filling statusof individual cells 118 within the cassette 34 can be stored on the RFIDtag. Thus, if the cassette 34 is removed and then reinserted into thesterilizer 10, or even into different sterilizer 10, the control system28 can be apprised of the status of each of the individual cells 118within the cassette 34. This allows the reuse of a partially usedcassette 34. Also, since the RFID tag 140 can hold more data than thebarcode 80, more data about the cassette 34, its contents andmanufacturing can be included thereon.

The spent collection box antenna 138 reads the spent collection box RFIDtag 142 to determine the presence or absence of the spent cassettecollection box 84. Other data such as a unique identifier for the box84, the capacity of the box 84, how many cassettes 34 are currently inthe box 84 and how many of the cells 118 therein are not empty can beincluded on the RFID tag 142. The control system 28 can track how manycassettes 34 have been ejected into the box to determine whether it hasroom for more spent cassettes 34. The antenna 138 can also read thecassette RFID tags 140 and count the number of cassettes 34 within thebox 84. When the box 84 is full the control system 28 alerts theoperator, as by a message on a screen. This message can also includeinformation regarding the cassettes 34 within the box 84. For instanceif not all of the cassettes 34 have been completely drained the operatorcan be informed of this to decide if more careful disposal may beindicated.

RFID technology is disclosed in the following U.S. patents, each ofwhich is incorporated herein by reference: U.S. Pat. Nos. 6,600,420;6,600,418; 5,378,880; 5,565,846; 5,347,280; 5,541,604; 4,442,507;4,796,074; 5,095,362; 5,296,722; 5,407,851; 5,528,222; 5,550,547;5,521,601; 5,682,143 and 5,625,341.

RFID tags typically comprise an antenna and an integrated circuitproduced in a thin form factor so they can be inconspicuously placedupon an object such as the cassette 34. Radio frequency energy sent bythe antennas 136 and 138 induce sufficient current within the antennainside the RFID tags 140 and 142 to power the integrated circuittherein. Some types of RFID tags carry their own power source and havelonger detection ranges, but that adds additional expense and isprobably not justified for the present use.

FIG. 16 shows the memory map for the memory within the RFID tags 140 and142. A 64-bit unique ID (UID) is set at the factory and cannot bechanged. Each RFID tag has its own unique number here. Sixty-four 32-bitblocks can be programmed by the user. These can be populated withinformation such as the manufacture date, expiration date, product ID,serial number, lot numbers, manufacturing location, filling status ofthe cells, strength and type of sterilant, time spent within thesterilizer 10 and the like.

Some sterilants are affected by heat. The RFID tag 140 can optionallyinclude temperature collection instrumentation and update thatinformation on the tag. If design temperature profiles are exceeded,such as a maximum temperature or excessive temperature over a timeperiod, then the cassette 34 can be rejected by the control system 28.Temperature measuring RFID tags are available from KSW-Microtec,Dreseden, Germany and from Identec Solutions, Inc., Kelowna, BritishColumbia, Canada. The interior of the sterilizer 10 where the cassette34 sits may be higher than ambient temperature. Thus, it may bebeneficial to put a maximum residence time (on board shelf life) on thetag 140 or even to update on the tag 140 this time the cassette hasalready spent inside of the sterilizer.

To test sterilant measuring equipment in the sterilizer 10, it may bebeneficial to provide cassettes 34 having water or other fluids withinone or more cells 118. Information regarding the special nature of thecassette 34 and its contents could be written onto the RFID tag.

During a cycle the sterilizer may only require part of the contents of acell 118. For instance, a particular cycle may call for the contents ofone and a half cells. The half filled nature of the cell 118 can bestored and then for the next cycle that cell 118 can be drained.

Preferably, communications between the tag 140 and 142 and thecontroller 132 are encrypted. For instance, the UID can be XORed with aneight-bit master key to form a diversified key for encrypting the data.Encryption algorithms such as the data encryption standard (DES) tripleDES, asymmetrical encryption standard (AES) or RSA security can be usedfor the encryption. The RFID controller 132 reads the data and thealgorithm in the control system 28 decrypts the data to reveal thestored information.

Other methods could be used to communicate between the cassette 34 andthe sterilizer 10. For instance information could be stored magneticallyon the cassette 34, such as with a magnetic encoded strip, and be readby a magnetic reader on the sterilizer. Wireless technology is becomingcheaper every day and it is envisioned that the cassette 34 couldinclude an active transmitter and a power source (i.e. a battery) suchas powered RFID tags or Bluetooth, 802.11b or other communicationstandard.

Further, the sterilizer 10 can be set up to communicate back to acentral source, such as the manufacturer or distributor thereof, andprovide information regarding its performance and the performance of thecassettes 34. Poorly performing cassettes 34 could be identified, as forinstance sterilant monitors in the sterilizer not detecting sterilantduring a cycle thus indicating some failure such as an empty cassette orbad sterilant therein. An improperly manufactured batch of cassettes 34could then be quickly identified and recalled. Such communication couldoccur over telephone, pager or wireless telephone networks or over theInternet.

Turning now also to FIGS. 17 and 18, the spent cassette collection box84 is preferably folded from a single sheet of printed cardboard orother stock. FIG. 17 shows an unfolded blank 150 and FIG. 18 shows theblank 150 folded to form the spent cassette collection box 84.

The blank 150 is divided by a series of fold lines (shown dashed) andcut lines into a bottom panel 152, side panels 154, end panels 156 andtop flaps 158. Folding tabs 160 extend laterally from the side panels154. Additional folding tabs 162 extend laterally from the end panels156. Barcodes 82 are printed on the side panels 154 in a position to bevisible in an upper interior corner of the spent cassette collection box84 when it is folded into the configuration shown in FIG. 18. A pair oftop flap locking tabs 164 extend from the top flaps 158 and fit intoslots 166 in the opposing top flap 158 when the box 84 is closed andinto slots 168 at the intersection of the bottom panel 152 and sidepanel 154 when the box 84 is opened.

To fold the box, the folding tabs 160 on the side panels 154 are foldedupwardly and then the side panels 154 are folded upwardly, therebyaligning the folding tabs 160 with the intersection between the bottompanel 152 and the end panels 156. The end panels 156 are then foldedupwardly and the end panel folding tabs 162 are folded downwardly overthe folding tabs 160. Locking tabs 170 on the end panel folding tabs 162fit into slots 172 at the intersection between the bottom panel 152 andend panels 156.

To place the box 84 into the open position as shown in FIG. 18, the topflaps 158 are folded downwardly to the outside and the locking tabs 164fitted into the slots 168. Once the box 84 is filled with spentcassettes, the top flaps 158 are folded upwardly over the top and thelocking tabs 164 can then be fitted into the slots 166 on the opposingtop flaps 158. This unique folding arrangement allows spent cassettes 34to fall into the open box 84 easily without the top flaps 158 getting inthe way and also allows easy closure of the box 84 once it has becomefilled.

While the invention has been particularly described in connection withspecific embodiments thereof, it is to be understood that this is by wayof illustration and not of limitation, and that the scope of theappended claims should be construed as broadly as the prior art willpermit.

1. A method of sterilizing a load of instruments in a sterilizercomprising the steps of: entering data regarding the nature of the loadinto a control system of the sterilizer; placing the load into a vacuumchamber in the sterilizer; based upon the data regarding the nature ofthe load entered into the control system, determining one or moreparameters of the cycle before running the sterilizer; running thesterilizer in accordance with the determined one or more parameters,including the step of running the sterilizer comprising: drawing avacuum upon the vacuum chamber with a vacuum pump; admitting a sterilantinto the vacuum chamber, the sterilant being substantially in its vaporphase within the vacuum chamber, and contacting the load with thesterilant.
 2. The method according to claim 1 the data comprises amaterial of one or more instruments in the load.
 3. The method accordingto claim 1 wherein the one or more parameters comprises an amount ofsterilant input to the vacuum chamber.
 4. The method according to claim1 wherein the sterilant is hydrogen peroxide and further comprising thestep of increasing the amount of sterilant input to the vacuum chamberfrom the sterilant source in response to the input of one or more of thefollowing materials: a polyamide, a polyurethane, a silicone rubber, apolyvinyl chloride, a polymethyl methyacrylate or a polysulfone.
 5. Themethod according to claim 1 wherein the one or more data inputs comprisea length and internal diameter of a lumen.
 6. The method according toclaim 1 wherein the one or more data inputs comprise a weight of theload.
 7. The method according to claim 1 wherein the one or moreparameters of the sterilization cycle comprises the concentration ofsterilant.
 8. The method according to claim 1 wherein the one or moreparameters of the cycle comprises time of exposure to the sterilant. 9.The method according to claim 1 wherein a user manually enters the dataregarding the nature of the load.
 10. The method according to claim 1wherein at least a portion of the data regarding the nature of the loadis read automatically from at least one of the instruments.
 11. Themethod according to claim 10 wherein the data is read from a bar code onthe instrument.
 12. The method according to claim 10 wherein the data isread from an RFID tag on the instrument.
 13. The method according toclaim 1 further comprising the step of measuring one of the parametersof the sterilization cycle and employing a feedback control loop toadjust one or more of the sterilization cycle parameters.
 14. The methodaccording to claim 1 and further comprising verifying efficacy ofsterilization with a biological indicator.
 15. The method according toclaim 1 and further comprising verifying efficacy of sterilization bymeasuring exposure level and integrating this over time to ensure thatat least a minimum integrated exposure of the load to the sterilant isachieved.
 16. The method according to claim 1 and further comprisingsaving a cycle outline for future use with a similar load.